This invention relates to telephone call sequencing equipment. More particularly, the present invention provides an automatic call answering and sequencing system for use with multiple incoming telephone lines connected to subscriber key service telephone units.
Telephones capable of receiving a call from a selected incoming line among numerous such lines are well known and widely used. One type of such a telephone is known as a key telephone or key service unit (KSU). These units are characterized by a handset and dial and a plurality of illuminable buttons or keys, each key being depressed to select the incoming line to which it is connected.
In key telephone systems, an unanswered incoming call is signalled to the telephone attendant by repetitive light flashes at the key of the line having the call and often by rings from the telephone bell as well. When the attendant picks up the handset and depresses the flashing key, the line having the incoming call is connected to the handset and the key become illuminated without flashing.
In telephone installations where there are only a few incoming lines or where there are many lines but few and infrequent incoming calls, the attendant or attendants are able to handle each call immediately upon arrival. However, where the system includes, e.g. ten or more incoming lines and at times all or many of the lines have unanswered incoming calls, a need has arisen to establish a priority sequence for the incoming calls so that the oldest call is brought to the attention of the attendant.
Concomitantly, a further need has arisen to answer the incoming calls shortly after they are received with a message explaining the delay and the fact that the call will be attended in the order of its arrival relative to other incoming calls. Thereafter, preferably, pleasant background music should be provided to the caller. Heretofore, no single system has met these requirements.
Highly complex call queuing systems have existed for routing calls on thousands of telephone lines to hundreds of operators, usually located at central offices of the telephone system. Such systems were vastly too complicated and expensive for use by telephone service subscribers having e.g. ten to one hundred sixty lines serviced by one or a few attendants. On the other hand, simple batch priority queuing systems for key service telephone installations have been proposed. In those systems all calls incoming within a predetermined time interval were indicated as priority calls with calls arriving during a second interval and later intervals not being so indicated to the attendant until all of the calls in the first batch were handled. Such batch systems were described in e.g. U.S. Pat. No. 3,752,936 to Morse. Those systems had the drawback that no priority was established between calls within each batch: when the attendant was unable to handle the calls in the batch rapidly, those calls were often handled out of order of receipt, which is the very same problem occuring with key telephones in the absence of any sequencing system.
Moreover, heretofore there has been no automatic answering and sequencing system available for addition to existing key service telephone installations through use of existing plug connections and without any internal modifications to the equipment of such installations. This has been a particularly significant drawback because of the reluctance of the telephone service companies to allow their equipment to be altered or modified in any way except to accomodate other of their own equipment.